Fix: resize GuestOS disk

[songponssw]

Try to fix: #1448

How Lima edit disk

• The limactl edit updates the disk value to the store. It does not resize disk image. Users have to manually resize by qemu-img
• Does not support --shrink (fails to start instance)

What I did

• create a limactl disk add command to add an existing qcow2 disk to Lima.
• To update GuestOS disk, before start instance, It adds a diffdisk of the instance to Lima, resize, and delete.

[songponssw]

This implementation works fine for increasing the disk size.
However, it returns an error when shrinking, as disk shrinking is not supported.

[AkihiroSuda]

Needs rebase

[songponssw]

Summary of Latest Review:

1. DiskDir is dedicated to additional disks.
   • I've updated the implementation by creating a new ResizeDiffDisk function, which directly resizes the diffdisk.
2. Calling inst.inspect() twice:
   • The editAction function returns instance.Start which doesn’t update the validated configuration in the store or the instance yet.
   • The second call to inst.inspect() is to apply the new configuration.
   • The first call to inst.inspect() checks whether the instance exists and is running.

[jandubois]

Note that #3513 moved the qemu-img functions to pkg/qemu/imgutil.

[AkihiroSuda]

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x104ceed71]

goroutine 1 [running]:
main.editAction(0xc0005acf08, {0xc0000ce960?, 0x4?, 0x104d7fff4?})
	/Users/runner/work/lima/lima/cmd/limactl/edit.go:139 +0x731
github.com/spf13/cobra.(*Command).execute(0xc0005acf08, {0xc0000ce910, 0x5, 0x5})
	/Users/runner/go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1015 +0xa94
github.com/spf13/cobra.(*Command).ExecuteC(0xc00059c008)
	/Users/runner/go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1148 +0x40c
github.com/spf13/cobra.(*Command).Execute(...)
	/Users/runner/go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1071
main.main()
	/Users/runner/work/lima/lima/cmd/limactl/main.go:41 +0x18

https://github.com/lima-vm/lima/actions/runs/14946273265/job/41989994774?pr=3437